The present invention relates generally to an apparatus and method for improved optical geometry for enhancement of fluorescence and spectroscopic detection in fluids. More particularly, the invention relates to an apparatus and method of fluorescence detection in fluids of marker proteins and analytes.
The conventional method of performing laser induced fluorescence measurements is to use a small transparent laboratory vessel known as a cuvette to contain the sample to be analyzed. A standard cuvette has dimensions of 1 cm×1 cm and is about 3.5 cm in height and sealed at the bottom. The cuvette is usually made of fused quartz or optical quality borosilicate glass. The cuvette is optically polished and sometimes has an antireflective coating. The cuvette is filled from an upper, open end that is usually equipped with a ground-in glass stopper.
To perform a measurement, the cuvette is filled with the liquid to be investigated and then illuminated with a laser focused through one of the cuvette's faces. A lens is placed in line with one of the faces of the cuvette located at ninety degrees from the input window to collect the laser-induced fluorescence light. Only a small volume of the cuvette is actually illuminated by the laser. This small volume produces fluorescence once affected by the laser, which is detrimentally reduced by the fact that the lens only picks up approximately ten percent of the fluorescence signal because of solid angle considerations. This is the current state of the art. It has been used for at least seventy-five years; even before the laser existed when conventional light sources were used to excite the fluorescence.